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prometheus/tsdb/blockwriter.go

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3.9 KiB

// Copyright 2020 The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package tsdb
import (
"context"
"errors"
"fmt"
"math"
"os"
"github.com/go-kit/log"
"github.com/go-kit/log/level"
"github.com/oklog/ulid"
"github.com/prometheus/prometheus/model/timestamp"
"github.com/prometheus/prometheus/storage"
"github.com/prometheus/prometheus/tsdb/chunkenc"
)
// BlockWriter is a block writer that allows appending and flushing series to disk.
type BlockWriter struct {
logger log.Logger
destinationDir string
head *Head
blockSize int64 // in ms
chunkDir string
}
// ErrNoSeriesAppended is returned if the series count is zero while flushing blocks.
var ErrNoSeriesAppended = errors.New("no series appended, aborting")
// NewBlockWriter creates a new block writer.
//
// The returned writer accumulates all the series in the Head block until `Flush` is called.
//
// Note that the writer will not check if the target directory exists or
// contains anything at all. It is the caller's responsibility to
// ensure that the resulting blocks do not overlap etc.
// Writer ensures the block flush is atomic (via rename).
func NewBlockWriter(logger log.Logger, dir string, blockSize int64) (*BlockWriter, error) {
w := &BlockWriter{
logger: logger,
destinationDir: dir,
blockSize: blockSize,
}
if err := w.initHead(); err != nil {
return nil, err
}
return w, nil
}
// initHead creates and initialises a new TSDB head.
func (w *BlockWriter) initHead() error {
chunkDir, err := os.MkdirTemp(os.TempDir(), "head")
if err != nil {
return fmt.Errorf("create temp dir: %w", err)
}
w.chunkDir = chunkDir
opts := DefaultHeadOptions()
opts.ChunkRange = w.blockSize
opts.ChunkDirRoot = w.chunkDir
opts.EnableNativeHistograms.Store(true)
h, err := NewHead(nil, w.logger, nil, nil, opts, NewHeadStats())
if err != nil {
return fmt.Errorf("tsdb.NewHead: %w", err)
}
w.head = h
return w.head.Init(math.MinInt64)
}
// Appender returns a new appender on the database.
// Appender can't be called concurrently. However, the returned Appender can safely be used concurrently.
func (w *BlockWriter) Appender(ctx context.Context) storage.Appender {
return w.head.Appender(ctx)
}
// Flush implements the Writer interface. This is where actual block writing
// happens. After flush completes, no writes can be done.
func (w *BlockWriter) Flush(ctx context.Context) (ulid.ULID, error) {
mint := w.head.MinTime()
// Add +1 millisecond to block maxt because block intervals are half-open: [b.MinTime, b.MaxTime).
// Because of this block intervals are always +1 than the total samples it includes.
maxt := w.head.MaxTime() + 1
level.Info(w.logger).Log("msg", "flushing", "series_count", w.head.NumSeries(), "mint", timestamp.Time(mint), "maxt", timestamp.Time(maxt))
compactor, err := NewLeveledCompactor(ctx,
nil,
w.logger,
[]int64{w.blockSize},
chunkenc.NewPool(), nil)
if err != nil {
return ulid.ULID{}, fmt.Errorf("create leveled compactor: %w", err)
}
id, err := compactor.Write(w.destinationDir, w.head, mint, maxt, nil)
if err != nil {
return ulid.ULID{}, fmt.Errorf("compactor write: %w", err)
}
return id, nil
}
func (w *BlockWriter) Close() error {
defer func() {
if err := os.RemoveAll(w.chunkDir); err != nil {
level.Error(w.logger).Log("msg", "error in deleting BlockWriter files", "err", err)
}
}()
return w.head.Close()
}